[Amps] Grid Vs cathode drive

[Peter Chadwick]

Hsu asked:
>Why many Amplifiers using cathode driven?why not grid ?<
My answer ( and it's doubtless open to argument) is two fold.
First, the majority of transceivers are of the 100 to 200 watt output level, so a grounded grid triode is a convenient way to go. Secondly, the FCC rules, certainly until recently and maybe still, for I don't know if they've implemented the changes they proposed, prevented manufacturers from selling in the US amplifiers with more than a certain amount of gain - the idea being to prevent CBers using illegal power. (And a vain hope that was!) So it made sense in power distribution to run about 13 dB of gain in the amplifier from a 100  watt driver, while for a lot of people,100 watts is a good power level to run anyway. And 13dB of gain in grounded grid is a reasonable number to get.
Given all this, the grounded grid triode amplifier is cheaper to produce, because you don't need a screen grid supply, and generally happens to be a bit more linear than tetrode, which you would need for a grounded cathode amplifier. I discount a neutralised triode grid driven amp these days......too complicated and thus expensive.

The downside is that you need tuned circuits in the cathode for decent linearity - I was always surprised at the 30L1 not having those.

The grounded cathode tetrode with grid swamping isn't to be discounted, but  can have the linearity improved with negative feedback, without too much difficulty.
Does this answer the question?
73
Peter G3RZP